Weapon-mounted firearm accessories have become an important tool for military, police, and civilian firearm users. Many firearm designs incorporate mounting rails for supporting these accessories, for example, rifles known as Modern Sporting Rifles. Using an accessory rail interface, a given accessory may be mounted to a variety of firearms or firearms platforms. Likewise, if a particular firearm includes a rail interface, a variety of accessories may be interchangeably mounted to the firearm. The interchangeability of accessories is of particular importance to military and law enforcement personnel attached to special operations units, as this allows a single firearm to be reconfigured to meet certain mission specific needs.
A number of rail-mounted firearm accessories can be used to facilitate aiming the weapon. Examples of such popular accessories for aiming a firearm include laser sighting devices, optical sighting devices such as riflescopes, and reflex sights. Laser sights project a laser light beam onto a target and can aid in shooting accuracy and speed, particularly in high pressure situations or when shooting at night or indoors in poorly lit environments. Although laser sights work well in low light conditions, in bright light conditions ambient light can easily overwhelm the dot generated on the target by the laser light source, making the dot difficult or impossible for the user to see. A laser sight also uses a relatively large amount of power, so the battery life for a laser sight is typically relatively short. Also, as with other sights, a laser sight is adjusted or sighted for a particular distance and wind condition. In some combat situations, the laser beam from a laser sight may also act as a targeting beacon for an adversary.
Reflex sights, also known in the art as a reflector sights or red dot sights, allows the user to look through a partially reflecting glass element and see an illuminated projection of an aiming point or reticle superimposed on the field of view
The sighting devices above and other sighting devices incorporate electronic components and are battery powered. When this is the case, the sighting device will fail to fully function if the battery drains or the electronic components fail. It is common for owners of modern sporting rifles to have on the upper rail, mounted back up iron sights as a further accessory for use in the event of failure of the laser, reflex or telescopic sight, or simply when it is not convenient or there is not time to use these sights.
Back up iron sights have a front post sight and a rear apertured windage sight, both individually mounted to the rail by way of a base with a clamp portion that adjustably clamps to the rail. A sight portion is often pivotally hinged to the base so that the sight portion may be laying along the rail when not in use and may be flipped-up for use. The sight portion being either a front sight post assembly or a rear apertured sight assembly.
The rear windage sight typically has a flippable rear sighting element having a first sight apertured portion and a second sight apertured portion, the element rotatable to allow positioning of one of the two apertured portions in the line of sight. Typically mechanical detents in the pivot connection secure the element in one or the other position.
Such back up iron sights are typically not made of iron as the name implies but are made either primarily or exclusively from metal or primarily from polymers. Polymer backup iron sights have the principle components injection molded providing an inexpensive product that may have the appearance of metal, a good “feel” due to polymers being softer and having less heat capacity than metals. Polymer backup iron sights are also lighter than metal, which is considered desirable by many users, and can also provide some shock absorption of minor impacts. Polymer bases that clamp to rails are less likely to damage (scuff, scratch, dent) the metal rails. Also, due to the resilience of polymers, a polymer rail clamp portion may be formed of a single injection molded piece that can, by way of the flexibility of polymer, be clamped to the rail by a tightening screw. There is a perception that polymer iron sights do not hold their adjustments as well as metal iron sights. Also polymer components may be damaged upon severe impact, their performance may deteriorate with extensive use and wear, and the polymer material may deteriorate over time. There is a perception that polymer backup iron sights have lesser quality.
When formed of metal the various components of the sights are generally stronger, more durable, generally will not deteriorate, and are perceived to hold their sight adjustment better. However the metal components of backup iron sights must be intricately machined, coated or painted, and assembled generally making all metal backup iron sights more expensive that such sights with the main components injection molded.
Any improvements to cost, function, durability of backup iron sights would be welcomed by consumers and manufacturers.